37

CHAPTER 3

EXPERIMENTAL INVESTIGATION

3.1 PROPERTIES OF MATERIALS USED

For designing the concrete mix, preliminary tests as per Bureau of

Indian standards (BIS) were conducted to find out the basic properties of

cement, fine aggregate and coarse aggregate used in this research. pH value of

potable tap water used was 7.54 (greater than 6) conforming to IS: 456-2000.

The test results are shown in Table 3.1.

Table 3.1 Test results of Concrete Ingredients

Material Property Average

Test results

Conducted test as per Indian Standards

BIS Cement Fineness test

(% residue on 90µ sieve) 1.26 IS:4031(part-1) 1996

Normal consistency 36% IS:4031(part-4)- 1988 Initial & Final setting time

125 & 230 Min

IS:4031(part-5)- 1988

Specific gravity 3.10 IS:4031(part-11)- 1988 Fine Aggregate

Fineness Modulus 2.42 IS: 383-1970 Zone confirm to II Specific gravity 2.65 IS: 2386 (Part III)

-1963 Moisture content 2.51% Coarse aggregate

Fineness Modulus 7.46 IS: 383-1970 Specific gravity 2.60 IS: 2386 (Part III)

-1963 Water absorption 1.11%

38

3.2 DESIGN OF REFERENCE CONCRETE MIX

Based on preliminary test results as presented in Table 3.1,

Reference concrete mix was designed as per Indian standard method by IS:

10262-1982. The relevant tables are presented in APPENDIX 1.

3.2.1 Design Stipulations

a) Grade of concrete = M20

b) Characteristic compressive strength

Required at 28 days = 20 MPa

c) Maximum size of aggregate =20mm

(Angular)

d) Degree of workability (Compaction factor) = 0.9

e) Degree of quality control = good

f) Type of exposure = mild

g) Specific gravity of cement ( sc ) = 3.10

h) Specific gravity of coarse aggregate ( Sca ) = 2.60

i) Specific gravity of fine aggregate ( Sfa ) = 2.65

j) Water absorption = 1.11%

k) Free surface of moisture of fine aggregate = 2.51%

l) Fine aggregate confirming zone = II

m) Entrapped air content (E air ) = 2%

(Table A.1.6 )

39

3.2.2 Design of Mix

Target Mean Strength

Target mean strength (ft) = fck + 1.65* S (S- Standard Deviation=4, Table A.1.1) = 20 + (1.65x4)

= 26.60 N/mm2

Water Cement Ratio

a. From graph w/c = 0.50 (Figure A.1.1 )

b. From type of exposure w/c = 0.55 (Table A 1.2)

c. Take least value of w/c = 0.50

Selection of Water and Sand Content

Table 3.2 shows the calculation of Adjustment of values in water

content and sand percentage by referring A 1.5. For 20mm size coarse

aggregate and sand confirming to zone II, Water content per cubic metre of

concrete was 186 kg and sand content as percentage of total aggregate by

absolute volume was 35% as per Table A1.3 and 1.4.

Table 3.2 Adjustment of values in water content and sand percentage

Change in condition Adjustment required in

Water content Sand content Sand zone – II – 0

For increasing compaction factor (0.90-0.80) = 0.1

+3

0

For decrease in water content ratio by (0.5-0.6) = -0.10

0

-2

+3% -2%

40

Required water content = 186 +3%

w = 191.58 kg

Required sand content = 35-2

P = 33%

Required cement content for w/c = 0.5,

= 191.58/0.5

C = 383.16 kg

Weight of Fine Aggregate (FA)

F.A = (1000 (1-Eair ) – w – C/sc) P x Sfa

F.A = (1000 (1-2/100) – 191.58 – (383.16/3.1)) x 33/100 x 2.65

= 581.38 kg/m3

Weight of Coarse Aggregate (CA)

C.A = (1000 (1-Eair ) – w – C/sc) (1 – P) x Sca

C.A = (1000 (1-2/100)– 191.58 – (383.16/3.1)) x (1 – 33/100) x 2.60

= 1158.11 kg/m3

Table 3.3 Water Adjustment for Actual Quantities of Different

Constituents

Quantity of water to be

changed

Water Cement Fine aggregate Coarse aggregate

191.58 383.16 581.38 1158.11 Water

absorption of C.A =1.1%

+12.73

–

– -12.73

Free surface moisture

FA =2.51% – 14.59 – +14.59 –

189.72 383.16 595.97 1145.38

41

The quantities of materials per cubic metre of concrete as presented

in Table 3.3 are summarised as below.

a) Cement = 383.16 kg

b) Fine aggregate = 595.97 kg

c) Coarse aggregate = 1145.38 kg

d) Water = 189.72 litres

Table 3.4 Calculation of Reference Concrete Mix Ratio

Cement Fine aggregate Coarse aggregate Water

383.16 595.97 1145.38 189.72

1 1.55 2.98 0.49

From Table 3.4, Reference Mix Ratio, RMX = 1: 1.55: 2.98: 0.49

3.3 PRELIMINARY INVESTIGATIONS

3.3.1 Optimum Dosage of Superplasticiser

Concrete consumption is 10 billion ton per year, which is

equivalent to 1 ton per every living person and hence judicious use of cement

has distinct economic and environmental effect reported by Nataraja et al

(2005). Another report by ACI 212.4R (1993) stated that superplasticisers are

added to economise the cement by simultaneous reduction of cement and

water content of the reference mix. Hence it is aimed to optimize the dosage

of superplasticiser by reducing cement and water content simultaneously,

keeping water-cement ratio constant, by the addition of superplasticiser to the

reference mix (RMX) at plastic and hardened states. Cement and water

content of the reference mix was reduced at a time simultaneously by 5%,

10%, 15% & 20% at each stage, superplasticiser was added at 0.4%, 0.8%,

42

and 1.2% by weight of cement. At each level of reduction of cement & water

with addition of superplasticiser, workability & strength values were

determined and compared.

There were 2 water reducers, 4 levels of cement reduction & 3

dosages of water reducers. Thus (2 x 4 x3 =) 24 mixes were made. The

following tests were conducted on the reference mix. Table 3.5 and Table 3.6

show mix details and quantities of materials used.

a) Slump test and Compaction factor test

b) 7 & 28-days compressive strength test

The quantity of materials required for conducting slump test,

compaction factor test and 7, 28-days compressive strength test were

calculated. The materials (cement, fine aggregate, coarse aggregate and water)

were weighed and taken separately. Cement and sand were first mixed, and

then coarse aggregate was added and thoroughly mixed to form a dry mixture.

Water was then added and mixed until a thorough homogenous mixture was

obtained. Slump test and compaction factor test were done simultaneously

and at the same time, three numbers of 150 mm size concrete cubes were cast

as per IS: 516-1959. The concrete cubes were removed from the moulds after

24 hours and placed in water for curing. At the end of 7th & 28th days from

the date of casting, the cubes were taken out and tested for their 7-days & 28-

days compressive strength in a 200 tonne capacity hydraulic compression

testing machine.

43

Table 3.5 Mix Details

Type MIX MIX DETAILS

REF

EREN

CE

MIX

W

ITH

Org

anic

supe

rpla

stic

iser

ORD1 RMX – 5 % W & C+0.4 % OSP

ORD2 RMX – 5 % W & C+0.8 % OSP

ORD3 RMX – 5 % W & C+1.2 % OSP

ORE1 RMX – 10 % W & C+0.4 % OSP

ORE2 RMX – 10 % W & C+0.8 % OSP

ORE3 R MX– 10 % W & C+1.2 % OSP

ORF1 RMX – 15 % W & C+0.4 % OSP

ORF2 RMX – 15 % W & C+0.8 %OSP

ORF3 RMX – 15 % W & C+1.2 % OSP

ORG1 RMX – 20 % W & C+0.4 % OSP

ORG2 RMX– 20 % W & C+0.8 %OSP

ORG3 RMX – 20 % W & C+1.2 % OSP

REF

EREN

CE M

IX

WIT

H

Nap

htha

lene

supe

rpla

stic

iser

NRD1 RMX – 5 % W & C+0.4 % NSP

NRD2 RMX – 5 % W & C+0.8 %NSP

NRD3 RMX – 5 % W & C+1.2 % NSP

NRE1 RMX – 10 % W & C+0.4 % NSP

NRE2 RMX – 10 % W & C+0.8 %NSP

NRE3 R MX– 10 % W & C+1.2 % NSP

NRF1 RMX – 15 % W & C+0.4 % NSP

NRF2 RMX – 15 % W & C+0.8 % NSP

NRF3 RMX – 15 % W & C+1.2 % NSP

NRG1 RMX – 20 % W & C+0.4 % NSP

NRG2 RMX– 20 % W & C+0.8 % NSP

NRG3 RMX – 20 % W & C+1.2 % NSP

44

Table 3.6 Quantity of Materials used per cubic metre of Concrete

without fibres

MIX Grade of cement

Wt cement per cubic metre of concrete

Fa/c Ca/c W/c %

Dosage of SP

RMX 53 383 1.55 2.98 0.49 0

ORD1 53 363 1.64 3.14 0.49 0.4

ORD2 53 363 1.64 3.14 0.49 0.8

ORD3 53 363 1.64 3.14 0.49 1.2

ORE1 53 345 1.72 3.31 0.49 0.4

ORE2 53 345 1.72 3.31 0.49 0.8

ORE3 53 345 1.72 3.31 0.49 1.2

ORF1 53 326 1.82 3.51 0.49 0.4

ORF2 53 326 1.82 3.51 0.49 0.8

ORF3 53 326 1.82 3.51 0.49 1.2

ORG1 53 306 1.94 3.74 0.49 0.4

ORG2 53 306 1.94 3.74 0.49 0.8

ORG3 53 306 1.94 3.74 0.49 1.2

NRD1 53 363 1.64 3.14 0.49 0.4

NRD2 53 363 1.64 3.14 0.49 0.8

NRD3 53 363 1.64 3.14 0.49 1.2

NRE1 53 345 1.72 3.31 0.49 0.4

NRE2 53 345 1.72 3.31 0.49 0.8

NRE3 53 345 1.72 3.31 0.49 1.2

NRF1 53 326 1.82 3.51 0.49 0.4

NRF2 53 326 1.82 3.51 0.49 0.8

NRF3 53 326 1.82 3.51 0.49 1.2

NRG1 53 306 1.94 3.74 0.49 0.4

NRG2 53 306 1.94 3.74 0.49 0.8

NRG3 53 306 1.94 3.74 0.49 1.2

3.3.2 Test Results and Discussion Tests were conducted on each mix to evaluate both workability and strength values.

45

3.3.2.1 Workability Tests

Slump and compaction factor values at various levels of reduction

are furnished in Table 3.7. It is found from slump test results that at 5%

reduction level of cement and water content, organic based superplasticiser

showed high slump values at the dosage level of 0.8 %. While increasing the

reduction level of cement and water content to 10% and 15%, sulphonated

naphthalene based superplasticiser showed higher slump values at the dosage

levels of 0.4 % and 0.8 %. But at 20% reduction level, very low slump values

were obtained at the dosage level of 0.4% and collapse slump was obtained at

higher dosages of 0.8% and 1.2% of both type of superplasticiser.

Compaction factor test showed that the concrete with naphthalene based

superplasticiser has medium and higher workability at the dosage level of

0.4% and 0.8%. At 20 % reduction level of cement and water content low

workability was obtained at the dosage level of 0.4 %. By overall observation,

it was found that at 15% reduction of cement and water content, concrete had

the highest slump values of 125 mm and 145 mm and compaction factor

values as 0.97 and 0.98 at the dosage level of 0.8% of organic and

naphthalene based superplasticiser respectively.

3.3.2.2 Compressive Strength Test

As the concrete had segregated and collapse slump occurred at 20%

reduction of cement and water content, it was decided to conduct only

strength test on concrete with both types of superplasticisers from 5% to15%

reduction of cement and water content. From the test results shown in Table

3.8, the compressive strength of concrete of reference concrete was found as

27.11 N/mm2 and 37.78 N/mm2 at 7 and 28 days curing respectively. It is

evident from this table that all the concrete mixes had the higher compressive

strength than the reference mix. Hence it is discriminated to choose the

46

concrete mix with low cement content which has higher strength than the

reference mix. Based on the results obtained from workability test and

compressive strength test, optimum dosage of superplasticiser was chosen

from the mix containing minimum dosage of superplasticiser at the level of

maximum reduction of cement and water content. It was found from Tables

3.7 and 3.8 that concrete mix, at the maximum reduction of cement and water

content by 15% with 0.8% dosage of superplasticiser, has higher workability

and compressive strength than reference concrete mix. Hence it was decided

to choose this mix to find optimum dosage of superplasticiser. Based on this

reduction level, the reference mix was revised as 1: 1.83: 3.51: 0.49 with

0.8% superplasticiser and is presented in Table 3.9. The dosage of

superplasticiser at this revised ratio is defind as the optimized dosage of

superplasticiser. Thus dosage of superplasticsier was optimized as 0.8%.

Consequent to the revised mix ratio it was found that about 58 kg of cement

was saved per cubic metre of concrete and hence economical.

Table 3.7 Workability Test Results

Phase Mix

Slump value in mm Compaction factor

Organic based- SP

Naph thalene

based-SP

Organic based- SP

Naph thalene

based- SP 1 REFERRENCE 10 10 0.9 0.9

2

R – 5 % W & C+0.4 % SP 10 15 0.95 0.89

R – 5 % W & C+0.8 % SP 140 85 0.98 0.91

R – 5 % W & C+1.2 % SP (Collapsed) (Collapsed) 1 0.96

R – 10 % W & C+0.4 % SP 40 20 0.92 0.97

R – 10 % W & C+0.8 % SP 80 140 0.93 0.96

R – 10 % W & C+1.2 % SP (Collapsed) (Collapsed) 0.98 0.96

R – 15 % W & C+0.4 % SP 30 25 0.94 0.95

R – 15 % W & C+0.8 % SP 125 145 0.97 0.98

R – 15 % W & C+1.2 % SP (Collapsed) (Collapsed) 0.98 0.94

R – 20 % W & C+0.4 % SP 0 10 0.89 0.911

R – 20 % W & C+0.8 % SP (Collapsed) (Collapsed) 0.93 0.94

R – 20 % W & C+1.2 % SP (Collapsed) (Collapsed) 0.98 0.99

47

Table 3.8 Compressive strength after 7 and 28 days curing

MIX

7 days strength MPa 28 days strength MPa Organic

based- SP Naphthalene

based- SP Organic

based- SP Naphthalene

based-SP Average %imp Average %imp Average %imp Average %imp

REFERRENCE 27.11 - 27.11 - 37.78 - 37.78 - R – 5 % W & C +0.4 % SP 33.48 23.5 35.11 29.5 46.81 23. 9 40.15 6.2 R – 5 % W & C +0.8 % SP 41.33 52.4 36.00 32.8 47.44 25.6 54.52 44.3 R – 5 % W & C +1.2 % SP 42.07 55.1 39.41 45.37 46.44 22.9 47.56 25.88 R – 10 % W &C +0.4 % SP 31.41 15.9 36.44 34.41 38.47 1.8 46.37 22.73 R – 10 % W &C +0.8 % SP 32.2 18.8 33.18 22.4 43.1 14 39.26 3.91 R – 10 % W &C +1.2 % SP 31.11 14.8 40.89 50.8 46.51 23.1 49.33 30.57 R – 15 % W &C +0.4 % SP 37.18 37.1 37.18 37.14 39.7 5.1 43.55 15.2 R – 15 % W &C +0.8 % SP 38.16 40.8 38.52 42.1 40.44 7 40.30 6.67 R – 15 % W &C +1.2 % SP 36.3 33.9 37.78 39.35 44.58 18 42.37 12.14

Table 3.9 Revised Mix ratio at 15 % simultaneous reduction of

cement and water

Cement Fine aggregate Coarse aggregate

Water

383.16 595.97 1145.38 189.72

325.67 595.97 1145.38 161.26

1 1.83 3.5 0.49

Reference Mix ratio RMX = 1: 1.55: 2.98: 0.49

Case A: Revised Mix Ratio OSP = 1: 1.83: 3.51: 0.49 +0.8% SP

Case B: Revised Mix Ratio NSP = 1: 1.83: 3.51: 0.49 +0.8% SP

48

3.4 EXPERIMENTAL PROGRAMME The programme was divided into two cases such as Case A and Case B and Figure 3.1 shows flow chart for experimental programme. Table 3.10 shows the materials used for entire experimental programme.

Table 3.10 Materials Used

Sl No DETAILS QUANTITY

1 Types of Superplasticiser 2

2 Dosage of Superplasticiser 0.8% ( optimized )

3 Types of Fibres 3

4 Volume of Fibre 0%, 0.2%, 0.4%, 0.6%, 0.8% & 1.0%

5 No. of Mixes Proposed 1 x 2 x 1 x 3x 6 = 36 Mixes

CASE A The performance of organic based superplasticiser was evaluated with fibres for mix ratio OSP based on the following phase of tests. PHASE I WORKABILITY TESTS

a) Slump Test

b) Compaction Factor Test

PHASE II STRENGTH TESTS (Before and After Thermoshock)

a) 7 & 28 Days Compressive Strength Test

b) 7 & 28 Days Split Tension Test

c) 28 Days Flexural Strength Test (Third point loading)

d) 28 Days Pull-out Test

e) 28 Days Impact Test

49

PHASE III DURABILITY TESTS (Before and After Thermoshock)

a) 28 Days Water Permeability Test

b) 28 Days Chloride Penetration Test

CASE B

The performance of Naphthalene based superplasticiser was

evaluated with Fibres for mix ratio NSP based on the following phases of

tests.

PHASE I WORKABILITY TESTS

a) Slump Test

b) Compaction Factor Test

PHASE II STRENGTH TESTS (Before and After Thermoshock)

a) 7 & 28 Days Compressive Strength Test

b) 7 & 28 Days Split Tension Test

c) 28 Days Flexural Strength Test (Third point loading)

d) 28 Days Pull-out Test

e) 28 Days Impact Test

PHASE III DURABILITY TEST (Before and After Thermoshock)

a) 28 Days Water Permeability Test

b) 28 Days Chloride Penetration Test

50

FLOW CHART FOR EXPERIMENTAL PROGRAMME

Figure 3.1 Flow Chart for Experimental Programme

OSP=RMX- (15% Water & Cement) + SP Organic Based

RMX-M20 Grade

AR Glass

Polyester

0.2 to 1% (OS1-OS5)

0.2 to 1%

(OG1-OG5)

0.2 to 1%

(OP1- OP5)

NSP=RMX- (15% Water & Cement) + SP Naphthalene Based

AR Glass

Polyester

Steel

0.2 to 1% (NS1- NS5)

0.2 to 1%

(NG1-NG5)

0.2 to 1%

(NP1-NP5)

Workability Test

Strength Test- Before & After Thermoshock Durability Test

Before & After Thermoshock

TEST

[1] Slump Test [2] Compaction Factor Test

[1]7 & 28 Days Compressive Strength Test on Cube and Cylinder specimen [2]7 & 28 Days Split Tension Test [3] 28 Days Flexural Strength Test [4] 28 Days Pull-Out Test [5] 28 Days Impact Test

1] 28 Day Water Permeability Test [2] Chloride Permeability Test.

Case A Case B

Fibres

Fibres

Steel

51

3.4.1 Mix and Specimen Preparation

All the ingredients were first mixed in dry condition in the concrete

mixer machine for one minute. Then, 75 percent of calculated amount of

water was added to the dry mix and mixed thoroughly for one minute. At this

stage, remaining 25 percentage of water mixed with superplasticiser was

poured into the mixer and mixed for one minute. Later, required quantities of

fibres were sprinkled over the concrete mix and mixer machine was allowed

to rotate for four minutes to get a uniform mix. The total mixing time was 7

minutes. Thus concrete mix was prepared.

To prepare specimen for various mixes, the quantity of materials

required and specimen details are presented in Tables 3.11, 3.12 and 3.13 for

various experimental works. The prepared concrete mix was poured in

moulds (after applying oil inside the mould) in three layers and each layer

was tamped 25 times by 16 mm diameter and 600mm long tamping rods and

then it was vibrated using table vibrater for 1minitue. The same procedure

was adopted for specimen preparation throughout this research work.

52

3.11 Details of Mix Proportioning

CASE Type MIX PROPORTIONS

Reference Mix RMX 1:1.55:2.89:0.49

Case A

Organic superplasticiser OSP RMX+0.8%Organic Based

SP O

rgan

ic b

ased

Sup

erpl

astic

iser

Stee

l fib

re OS1 OSP+0.2%SF

OS2 OSP+0.4%SF OS3 OSP+0.6%SF OS4 OSP+0.8%SF OS5 OSP+1%SF

AR

Gla

ss

Fibr

e OG1 OSP+0.2% ARGF OG2 OSP+0.4%ARGF OG3 OSP+0.6% ARGF OG4 OSP+0.8% ARGF OG5 OSP+1%ARGF

Poly

este

r Fib

re

OP1 OSP+0.2% PF OP2 OSP+0.4% PF OP3 OSP+0.6% PF OP4 OSP+0.8% PF OP5 OSP+1% PF

Case B

Naphthalene superplasticiser NSP

RMX+0.8% Naphthalene Based SP

Nap

htha

lene

bas

ed S

uper

plas

ticis

er w

ith

Stee

l fib

re NS1 NSP+0.2%SF

NS2 NSP+0.4%SF NS3 NSP+0.6%SF NS4 NSP+0.8%SF NS5 NSP+1%SF

AR

Gla

ss

Fibr

e

NG1 NSP+0.2% ARGF NG2 NSP+0.4% ARGF NG3 NSP+0.6% ARGF NG4 NSP+0.8%ARGF NG5 NSP+1% ARGF

Poly

este

r Fib

re

NP1 NSP+0.2% PF NP2 NSP+0.4% PF NP3 NSP+0.6 %PF NP4 NSP+0.8 % PF NP5 NSP+1% PF

53

Table 3.12 Quantity of Materials used per cubic metre of Concrete

MIX Grade of cement

Wt of cement per

cubic metre of concrete

Fa/c Ca/c W/c %

Dosage of SP

% Vol of Fibre

Aspect Ratio-Fibre

Density of

Fibre t/m3 *

RMX 53 383 1.55 2.98 0.49 0 0 0 0 OSP 53 325.5 1.83 3.51 0.49 0.8 0 0 0 OS1 53 325.5 1.83 3.51 0.49 0.8 0.2 80 7.76 OS2 53 325.5 1.83 3.51 0.49 0.8 0.4 80 7.76 OS3 53 325.5 1.83 3.51 0.49 0.8 0.6 80 7.76 OS4 53 325.5 1.83 3.51 0.49 0.8 0.8 80 7.76 OS5 53 325.5 1.83 3.51 0.49 0.8 1 80 7.76 OG1 53 325.5 1.83 3.51 0.49 0.8 0.2 860 2.6 OG2 53 325.5 1.83 3.51 0.49 0.8 0.4 860 2.6 OG3 53 325.5 1.83 3.51 0.49 0.8 0.6 860 2.6 OG4 53 325.5 1.83 3.51 0.49 0.8 0.8 860 2.6 OG5 53 325.5 1.83 3.51 0.49 0.8 1 860 2.6 OP1 53 325.5 1.83 3.51 0.49 0.8 0.2 267 1.33 OP2 53 325.5 1.83 3.51 0.49 0.8 0.4 267 1.33 OP3 53 325.5 1.83 3.51 0.49 0.8 0.6 267 1.33 OP4 53 325.5 1.83 3.51 0.49 0.8 0.8 267 1.33 OP5 53 325.5 1.83 3.51 0.49 0.8 1 267 1.33 NSP 53 325.5 1.83 3.51 0.49 0.8 0 0 0 NS1 53 325.5 1.83 3.51 0.49 0.8 0.2 80 7.76 NS2 53 325.5 1.83 3.51 0.49 0.8 0.4 80 7.76 NS3 53 325.5 1.83 3.51 0.49 0.8 0.6 80 7.76 NS4 53 325.5 1.83 3.51 0.49 0.8 0.8 80 7.76 NS5 53 325.5 1.83 3.51 0.49 0.8 1 80 7.76 NG1 53 325.5 1.83 3.51 0.49 0.8 0.2 860 2.6 NG2 53 325.5 1.83 3.51 0.49 0.8 0.4 860 2.6 NG3 53 325.5 1.83 3.51 0.49 0.8 0.6 860 2.6 NG4 53 325.5 1.83 3.51 0.49 0.8 0.8 860 2.6 NG5 53 325.5 1.83 3.51 0.49 0.8 1 860 2.6 NP1 53 325.5 1.83 3.51 0.49 0.8 0.2 267 1.33 NP2 53 325.5 1.83 3.51 0.49 0.8 0.4 267 1.33 NP3 53 325.5 1.83 3.51 0.49 0.8 0.6 267 1.33 NP4 53 325.5 1.83 3.51 0.49 0.8 0.8 267 1.33 NP5 53 325.5 1.83 3.51 0.49 0.8 1 267 1.33

* 1 t/m3 = 9.81 kN/m 3

54

Table 3.13 Specimen Details

Test Thermo Shock period

Type of specimen

Dimension of specimen

mm

No of specimen

Compressive Strength Test after 7&28 days curing

1 &2 hrs Cube 150x150 33 x 4 x 3=396

2 hrs Cylinder 150x300 33 x 3 x 3=297

Split Tension Test after 7&28 days curing

2 hrs Cylinder 150x300 33 x 3 x 3=297

Flexural Strength Test after 28 days curing

2 hrs Beams 500x 100x100 33 x 2 x 3=198

Pull-Out Test after 28 days curing

- Cube 150x150 33 x 1 x 3=99

Impact Test after 28 days curing

2 hrs Disc 150 Dia with 62.5 thick 33 x 2 x 3=198

Water Permeability Test after 28 days curing 2 hrs Cube 150x150 33 x 2 x 3=198

Rapid Chloride Permeability Test after 28 days curing

2 hrs Disc 95 Dia with 50mm thick 33 x 2 x 3=198

Total 1881

3.5 EXPERIMENTAL WORK

The experimental works conducted includes workability test,

strength test and durability test as described in section 3.4.

3.5.1 Workability Tests

Workability tests are conducted for concrete at fresh state. At this

stage, concrete should have good workability. At construction place, good

workable concrete will have no segregation while handling, no loss of

homogeneity while placing, easiness for compacting and finishing.

Workability of concrete is obtained by conducting slump and compaction

factor tests.

55

3.5.1.1 Slump Test

The test procedure was used as given in IS: 1199-1959. Slump test

was conducted using a standard slump cone of bottom diameter 200 mm top

diameter 100 mm and of height 300 mm. Concrete mix was prepared and

filled in slump cone as described in section 3.4.1. After filling the concrete,

slump cone was then gently and vertically raised. The concrete settles under

its own weight and vertical distance from its original level to new level after

subsidence was measured. This difference in height is known as slump. From

this test, slump value was measured for all the mixes.

3.5.1.2 Compaction Factor Test

The test procedures were used as given in IS: 1199-1959. The

value of compaction factor was found by using a standard compaction factor

apparatus, which consists of an upper hopper, lower hopper & bottom

cylinder. Concrete mix was prepared and filled in upper hopper. Then trap

door at the bottom of the upper hopper was opened to allow the concrete to

fall into lower hopper. After the concrete comes to rest , trap door of lower

hopper was opened to allow concrete to fall into the cylinder. The weight of

the concrete in cylinder was determined and this is known as Weight of

partially compacted concrete. The cylinder is refilled with concrete from the

same sample in layers and tamped for full compaction. Then the weight of the

refilled concrete in cylinder was determined and this is known as Weight of

fully compacted concrete. From this test, compaction factor was measured for

all the mixes from equation 3.1.

Weight of partially compacted concrete Compacting Factor = (3.1)

Weight of fully compacted concrete

56

3.5.2 Strength Tests

Tests were conducted on hardened concrete to find out

Compressive strength, Split tensile strength, Flexural strength, Pull-out test

and Impact strength as per the procedure given below and the results are

presented in chapter 4.

3.5.2.1 Compressive Strength Test

The test procedures were used as given in IS: 516-1979. Steel

moulds of size 150 x 150x 150 mm were used for casting the specimens.

Concrete mix was prepared and specimens were prepared as per section 3.4.1.

Specimens were allowed for curing in a curing tank for a period of 7days &

28 days. After the curing period the specimens were removed from the

curing tank and the surfaces were wiped. The dimensions of the specimens

and the weight of the specimens were noted down with accuracy. Area of the

specimen (A) was calculated from its dimensions. Weight of all the specimens

were in between 8.4 to 8.8 kg. A 200 tonne hydraulic compression testing

machine was used. Then specimen was placed in such a manner that the load

is applied to opposite side of cubes as caste. The load was applied at the rate

of 140 kg/cm2/minute till the cube breaks. Maximum load (W) is recorded at

the time of concrete failure. Same procedure was adopted for all the mixes

and compressive stress was calculated from equation 3.2.

Compressive Stress = AW (3.2)

3.5.2.2 Split Tension Test

The split tension test is a method of determining the tensile strength

of concrete. In its most common form, a cylinder is compressed along two

57

opposite generators until it splits across the diametrical plane connecting the

loading strips. The test procedures were used as given in IS: 516-1979. Steel

moulds of diameter 150mm and of height 300 mm were used for casting the

specimens. Concrete mix and specimens were prepared as per section 3.4.1.

Specimens were allowed for curing in a curing tank for a period of 7days &

28 days. The dimensions of the specimens and the weight of the specimens

were noted down with accuracy. Weight of all the specimens were in between

13.2 to 13.6 kg. Then specimen was placed horizontally between the loading

surface of the 200 tonne hydraulic compression testing machine and the load

was applied till the specimen splitted into two halves. The ultimate load at the

time of failure was noted. Same procedure was adopted for all the mixes and

split tensile stress was calculated from equation 3.3. Figure 3.2 shows set up

for split tensile test.

Figure 3.2 Split Tensile Test Set Up

Split Tensile Strength = DL

P2

(3.3)

Where, P is the load on the cylinder L is the length of the cylinder D is the diameter of the cylinder

P

Poisson’s Effect

Concrete Cylinder

58

3.5.2.3 Flexural Strength Test

The test procedures were used as given in IS: 516-1979. Steel

moulds of size 500 x100 x 100 mm were used for casting the specimens.

Concrete mix and specimens were prepared as per section 3.4.1. Specimens

were allowed to cure in a curing tank for a period of 28 days. The dimensions

of the specimens and the weight of the specimens were noted down with

accuracy. Weight of all the specimens were in between 12.5 to 12.8 kg The

testing machine was provided with two rollers of 38mm diameter on which

the specimens were placed and the rollers were spaced such that the distance

between two rollers was 400 mm as shown in Figure 3.3. The load was

applied through two similar rollers mounted at the third points of the

supporting span, at a distance of 133.3 mm centre to centre. The load was

divided equally between the two loading rollers and the rollers were mounted

in such a manner that the transverse load was applied along the longitudinal

axis and without subjecting specimen to any torsion stresses.

The load was applied with out shock and increasing continuously at

a rate such the extreme fibre stress increase at approximately 0.7kg/sqcm/ min

that is at a rate of loading 180 kg/min. The load was applied until the

specimen failed and maximum failure load applied was recorded. Same

procedure was adopted for all the mixes.

Figure 3.3 Flexural Strength Test Set Up

w

133.3 133.3 133.3 50 50 Dimensions are in mm

59

After the failure of this specimen, the position of fracture was

noted. If ‘a’ is the distance between line of fracture and the nearer support and

if it is greater than 133mm (that is, middle third of the span), the Flexural

Stress (FS) or modulus of rupture of the specimen was calculated from

equation 3.4

Flexural Stress = 2BDWL (3.4)

Where, W is the load applied L is the length of the beam B is the breadth of the beam and D is the depth of the beam. 3.5.2.4 Pull-Out Test

The test procedures were used as per in IS: 2770-1967. Steel moulds of size 150 x 150x 150 mm were used for casting the specimens. Concrete mix and specimens were prepared as per section 3.4.1. A single reinforcing bar was embedded vertically along a central axis in each prepared specimen as shown in Figure 3.4. The diameter of the bar used was 16mm. The bar should be free from grease, paint or other coatings which would affect the bond between reinforcing bar and concrete. The bar was projected down such that the clear distance between the rod and the bottom face of the cube was about 10 mm and was projected upward from the top face with a convenient distance necessary to provide sufficient length of bar to extend through the bearing blocks and the support of the testing machine and to provide an adequate length to be gripped for application of load. Then, the specimen was mounted on a universal testing machine in such a manner that the bar is pulled axially from the cube. The load was applied to the reinforcing bar at a rate not greater than 2250 kg/mm. The loading was continued until the enclosing concrete fails and the corresponding load was

60

noted. Same procedure was adopted for all the mixes and bond stress was calculated from equation 3.5.

Bond stress =dLP

(3.5)

Where P is the load applied

L is the length of the steel bar embedded in the cube

d is the diameter of the steel bar

F ib r eC o n c r e te C u b e

P

Figure 3.4 Pull-Out Test Set Up

3.5.2.5 Impact Strength Test

The test procedures were used as per ACI committee report

544.2R-89. Concrete structures are subjected to short duration (dynamic)

loads. Such loads originate from sources such as impact from missiles and

projectiles wind gusts, earthquakes and machine vibrations reported by

Gopalarathinam (1986). The dynamic response to impact is complex and is

dependent on many factors such as velocity of striker, contact area, size of the

target structure, material behaviour of the striker on the structure etc. It is

necessary to estimate the maximum dynamic energy absorption capacity

which a structure would sustain if it were involved in a collision with another

body or subjected to explosive loads. The review of literature indicates that

61

there were four different methods available to test the impact resistance of

cementitious and hybrid reinforced cementitious materials namely, explosive

test, projectile impact test, drop weight impact test and Charpy impact test.

Drop weight impact test method also known as repeated impact test was the

simplest among all the four methods and was devised by Schrader.

Figure 3.5 Section Through Test Equipment for Impact Strength

In drop weight method the number of blows necessary to cause

prescribed level of distress in the specimen is counted and this gives the

quantitative estimate of energy absorbed by the specimen at the distressed

level. Concrete test specimen is a cylindrical disc having 150mm diameter

and 62.5 mm thickness as shown in Figure 3.5. The specimen was coated on

the bottom with a thin layer of grease and placed at the base plate. Elastomer

pads were placed between specimen to restrict movement of the specimen

during testing. A drop hammer was used to apply the impact load. The

weight of the hammer was 45N. The number of blows required by the

dropping hammer through a height of 457mm to cause the first visible crack

and to cause ultimate failure were recorded. Each blow represents 20.2 Nm of

energy absorbed by the specimen. The first crack was based on visual

observation. Painting the surface of the test specimen facilitated the

Dimensions are in mm

62

identification of this crack. Ultimate failure is defined in terms of number of

blows required to open the crack in the specimen into three or more fractured

pieces and butting against the legs of base plate. Same procedure was adopted

for all the mixes and Energy absorption capacity was calculated from

equation 3.6.

Energy absorption capacity= Load x distance x No. of blows required for cracking/failure (3.6) Where Load = 45 N Distance = 457 mm 3.5.2.6 Reserve Strength

It is defind as strength or energy stored or absorbed beyond first

crack strength upto ultimate failure of concrete. It is assumed that concrete

undergoes elastic deformation upto first crack and concrete undergoes

inelastic response beyond first crack. The measure of reserve capacity gives

ability of concrete to resist inelastic deformation. This is the post cracking

strength of concrete. Percentage of reserve strength is calculated from

equation 3.7.

Percentage of reserve strength = 100xEA

EAEA

Icrack

IcrackUlt

(3.7)

Where EAUlt - Energy absorption at ultimate failure EAI crack - Energy absorption at first crack

3.5.3 Durability Tests

Nowadays durability of concrete is a subject of major concern in many countries. It is a wrong notion that strong concrete is always a durable concrete. Strong concrete may be structurally strong enough to withstand the external load. But such structure may fail by environmental effects. For

63

example, while it is structurally possible to build a jetty pier in marine conditions with 20 MPa concrete, environmental condition or exposure may lead this structure to a disastrous consequences. Durable concrete will retain its original form, quality and serviceability when exposed to its environment. Hence it is necessary to conduct durability tests on concrete. Under this study, water permeability and chloride penetration test was conducted on concrete. Recent revision of IS: 456-2000 gives more emphasis on durability of concrete apart from strength.

3.5.3.1 Permeability Testing of Concrete

Water permeability test procedures were carried out as per the standard IS: 3085-1965. Though much research has been performed to identify, investigate, and understand the mechanical traits of fibre–reinforced concrete, relatively little research has concentrated on the transport properties of this material. Material transport properties, especially permeability, affect the durability and integrity of a structure. Permeability of concrete is due to internal movement of water or other fluids, transporting aggressive agents through the pore structure of the concrete. High permeability, due to porosity or cracking, provides an ingress for water, chlorides and other corrosive agents. If such agents reach reinforcing bars within the structure, the bars get corroded. Hence the study of water permeability of concrete is very important.

To conduct the permeability test cubes of side size 150mm were

cast and water cured for 28 days. After 28 days of curing, specimens were

placed properly in the six cell permeability apparatus. Figure 3.5 shows

section of permeability cell. A Rubber sheet of 8mm thick and 150 x 150mm

size with a central hole of 100 x 100mm was taken. This rubber sheet was

then placed on the top & bottom surface of the cube in the permeability cell.

Cover plate was then tightened properly. The rubber sheet acts as a washer

and prevents the leakage of water through the annular space between

64

specimen and cell. Suitable arrangements were made for supplying

compressed air at 10 kg/cm2 to the cell by a compressor with an adequate

supply of cleaned de-aired water for constant supply of pressurized water.

Collecting jar was placed under the concrete specimen to collect the

discharged water from the concrete. The test was conducted continuously for

100hrs. After 100hrs cubes were then taken out from the cell for finding the

coefficient of permeability. There are two common methods for the

evaluation of co-efficient of permeability of concrete and they are steady flow

method and depth of penetration method. During the test if there is

permeability of water, the coefficient of permeability can be calculated using

the steady flow method and if there is no permeability of water, the

coefficient of permeability can be calculated using depth of penetration

method. In this method cubes are splitted and depth of penetration is

measured in the specimen.

Figure 3.6 Enlarged Section of Permeability Cell

While conducting the test, it was monitored for the permeability

of water through the specimen. It was found that there was no permeability of

65

water through the concrete. Hence co-efficient of permeability (K) was found

by depth of Penetration method from equation 3.8. In this method, cubes were

splitted and depth of penetration was measured in the specimen at different

locations and average depth of penetration was obtained. The method was

developed by Valenta referred in Neville (1981), equivalent to that used in

Darcy’s Law.

K = TH2

PD 2

(3.8)

Where K = Co-efficient of permeability in m/s D = Depth of penetration in cm

P = Porosity of concrete measured as a fraction T = Time in sec H = Pressure head=100m

3.5.3.2 Porosity Calculation

The mix ratio of reference concrete is 1:1.55:2.98:0.49. Neville

and Brooks (2008) have dealt in detail the derivation of the formula to find

the porosity of concrete. Porosity of concrete (p) was calculated using the

formula 3.9.

ca

cw

cA

S1

cA

S1317.0

cah17.0

cw

pco

ca

f

fa

(3.9)

Where w/c- Water- Cement ratio h- Degree of hydration a- Volume of entrapped air S- Specific gravity of cement 3.10 Sfa - Specific gravity of fine aggregate 2.65 Sca - Specific gravity of coarse aggregate 2.60

66

Ac, Af, Aco - Proportions of cement, fine aggregate and coarse aggregate in the reference mix ratio RMX. Air content of the concrete is calculated from equation 3.10. The

percentage of air content to total volume is 2% (from section 3.2)

02.0a

cw

SA

SA

SA

ava

ca

co

fa

fc

(3.10)

Here, denominator represents the total volume of concrete For w/c=0.49, Degree of hydration h=68%

The volume of air “a” was given by

a = 0.052

Porosity (p) of the concrete was therefore from equation 3.9

ca

cw

cA

S1

cA

S1317.0

cah17.0

cw

pco

ca

f

fa

Thus Porosity of concrete p = 0.149

3.5.3.3 Rapid Chloride Penetration Test

Corrosion of reinforcement in reinforced concrete structures is one of the most hazardous durability problems. One of the principal sources of this problem is the ingress of chloride ions into porous concrete. Movement of ions in a porous medium under a concentration gradient is called diffusion. It

02.0a49.015.158.033.0

a

052 .049. 06 .2

98.265. 255. 1317. 0

052.0)68.0 (X17. 049. 0p

67

is often necessary to ascertain the impermeability of concrete to chloride ions as a quality control measure and also for assessment of improvements effected in properties of new concrete. Measurements of chloride diffusion co-efficient requires a long time for establishment of steady state conditions. Therefore a direct current (DC) potential is usually applied to accelerate migration of ions.

Rapid chloride penetration test (RCPT) was performed as per ASTM C 1202 to determine the electrical conductance of the Fibrous concrete at the age of 28 days curing. The test method consists of monitoring the amount of electrical current passed through 50mm thick slices of 95 mm diameter of cylindrical specimens for duration of six hours.

The RCPT apparatus consists of two reservoirs as shown in Figure 3.7. The specimen was fixed between two reservoirs using an epoxy bonding agent to make the test setup leak proof. One reservoir was filled with 0.3N Sodium Hydroxide solution and the other reservoir with 3 % Sodium Chloride solution. A DC of 60V was applied across the specimen using two copper des and the current across the specimen was recorded at 30 minutes intervals for duration of six hours. The total charge passed in coulombs during this period was calculated from equation 3.11 given in ASTM C 1202.

Figure 3.7 Chloride Penetration Test Set Up

68

Q = 900 ( I0 + 2 I30 + 2 I60 +………+ 2 I330 + 2 I360 ) (3.11)

Where,

Q = Charge passed (coulombs)

I0 = Current immediately after voltage was applied

It = Current at ‘t’ minutes after voltage was applied

The higher amount of electric charge passed in the test represents

the higher penetrability of the concrete to chloride ions. The concrete quality

(degree of chloride ion penetrability) can be assessed based on the limits as

given in ASTM C 1202 and it is presented in Table 3.14.

Table 3.14 Chloride ion penetrability based on charge passed

Charge Passed (Coulombs) Chloride ion penetrability >4000 High

2000-4000 Moderate 1000-2000 Low 100-1000 Very Low

<100 Negligible

3.5.4 Testing of Concrete After Thermoshock

Generally concrete is incombustible and has good fire resistance

properties. When concrete is subjected to continuous exposure to elevated

temperature under fire and sudden cooling by water, it leads to thermoshock.

Thermo shock which may significantly influence the dehydration of the

hydrated calcium silicate, the release of chemically bound water, thermal

incompatibility between the aggregates & cement paste and these are the main

detrimental factors under heating. During exposure to heat, aggregate expands

and cement matrix shrinks due to loss of moisture and drying shrinkage type

69

stresses will be created. If it exceeds drying shrinkage capacity of concrete,

micro cracks are developed at interfacial transition zone and propagate. Such

micro cracks lead to decrease its strength and durability of concrete. Hence

experimental study of concrete before and after thermoshock is made under

strength as well as durability aspects.

The residual strength is the strength of heated and subsequently

cooled concrete specimen. That is strength of concrete after thermoshock is

referred as residual strength (TRS). The residual strength of concrete after

subjected to elevated temperature is generally less than its RMX strength. The

percentage variation in residual strength is calculated from equation 3.12

Percentage variation Residual strength with RMX =

100x

RMXRMXTRS (3.12)

3.5.4.1 Testing Procedure

The specimens were placed inside the hot air oven and were heated

to a temperature of 200o C and the temperature was sustained for two hours.

After two hours, the specimens were taken out and were immediately

quenched in water to simulate the thermo shock effect. The cooling was done

for about half an hour. The specimens were then tested for its residual

strength. Percentage change in strength was calculated by comparing the

strength of specimens without thermo shock.

Cube and cylinder specimens were used to test for compressive

strength. Thermoshock test was conducted after 1 hr and 2 hr exposure to

heat. Similarly test was conducted after 2hrs exposure to heat in case of

cylinder specimens. Thermoshock test was performed for specimen under

split tension test, flexure test, impact test, water permeability test and chloride

penetration test after 2 hrs exposure to heat.